The invention concerns a clock movement and, in particular, a clock movement having a circuit board held by a supporting plate within a split-shell housing; a hands movement is arranged in front of the supporting plate, while a gear movement is disposed behind the supporting plate and mounted thereon.
A clock movement of this type is known from U.S. Pat. No. 3,945,192. This movement has proven successful especially in terms of its manufacturing advantages over prior movements wherein the movement is located between two plates spaced apart by means of posts. In the U.S. patent the works are to be mounted on both sides of a single sheet support plate. A disadvantage, however, involves the great structural depth in the direction of the hands and gear shafts, as well as the use of the circuit board for both carrying the electric drive actuating circuit, and as a functional structural part for bearing gear support; this type of usage involves special requirements in relation to the fabrication material and the manner of installation of the circuit board.
It is known from U.S. Pat. No. 4,263,667 to use in a clock movement of this generic type a step motor as an electromechanical transducer. The stator is mounted, as are the other structural elements of the timekeeping, quartz stabilized drive circuit, on the circuit board, in particular by means of connecting pins passing through the circuit board. The stator is soldered to those pins on the side of the board laminated to form conductor bars. The step motor rotor is disposed in the rotor opening between the stator sheet pole shoes and is equipped with a flying bearing support on a pin which is anchored parallel to the front shell of the two-shell housing of the clock movement. The gear and hands movement is mounted on an intermediate plate positioned on posts in the front shell of the housing and is bearingly supported between the front wall of the front housing shell and the rear wall of the rear housing shell. This movement has proven itself in millions of cases. A disadvantage relates to the relatively great depth of installation required in particular by the circuit board extending parallel to the work axis, and the need for high manufacturing accuracy as a consequence of the distribution of the bearing locations of the movement over different structural parts to be joined frictionally to each other, which may have a detrimental effect on the efficiency of the step motor and the configuration of the gears, and on the generation of noise.
A basically similar clock movement is known from U.S. Pat. No. 3,943,695, in which the gear and hands movement is mounted in a conventional manner between two plates spaced apart by posts, with one of the plates being equipped with studs for the positioning of a rivetted step motor stator. The circuit board for the electronic drive circuit is fastened parallel to the step motor stator in a spaced apart manner on extensions of the plate posts. To connect the coil with the circuit board, this distance is bridged by a coil terminal pin, anchored in the coil bobbin carried by the stator sheet. The step motor rotor is supported on the bottom of a pot-like recess in the plate to which the step motor stator is rivetted, with a separate bridge being provided as the second bearing for the rotor shaft. The second bearing is fastened between the circuit board and the plate. This movement again has the disadvantage of a substantial depth of installation parallel to the works axis and the afore-mentioned disadvantages of the mounting of the drive gears between several plates.
In U.S. Pat. No. 4,175,374 there is provided a bearing support in an intermediate plate and in the rear housing shell. The step motor stator is positioned both on the intermediate plate and on the rear shell of the housing. The circuit board is inserted parallel to the gear axles. These features lead to an undesirably great structural depth in the direction of the works axis, together with a significant effort in relation to assembly technology.
In view of these disadvantages it is the object of the invention to develop a clock movement of the aforementioned basic type, while retaining the manufacturing and functional advantages resulting from the single plate concept, so that an especially flat and easily assembled configuration of a gear and hands movement is provided. The arrangement should be capable of being readily inspected in case of a malfunction and easily repaired, and driven by a step motor with high functional safety and low noise generation.